help with perculas

I am trying to find someone that can give me some help. I have put out
about $200 on percula's only to have them all die on me. I have a 55G
tank with a tidal wave wet/dry. Water tests are all very good with
ammonia and all testing at 0 and not having any problems with the
other fish or crabs in the tank.
I have the Clowns for 2 to 3 weeks, then all of a sudden the will stop
eating, start to breath rapid and then die off. Have tired putting
them in a hospital tank with Copper safe and fresh water dip that have
not helped. These have all been tank-raised clowns. Any help would be
greatly approached.
Archie